Method and apparatus for controlling the injection of particulate material into the tuyere zone of a blast furnace



April 3, 1965 E. v. SCHULTE ETAL 3,173,234

METHOD AND APPARATUS FOR CONTROLLING THE INJECTION OF PARTICULATE MATERIAL INTO THE TUYERE ZONE OF A BLAST FURNACE Filed July 30, 1963 INVENTORS.

5/. W000 v. SCHULTZ, JOHN F. FARNJWOETl-l.

United States Patent 3,178,234 METHOD AND APPARATUS FOR CONTRQL- LING THE lNZECTION 0F PARTKIULATE MATERIAL INTO THE TUYERE ZQNE @F A BLAST ACE Elwood V. Schulte and John F. Farnsworth, Pittsburgh, Pa, assignors to Koppers Company, Inc, a corporation of Delaware Filed July 30, 1963, Ser. No. 298,758 4 Claims. (Ci. 302-17) This invention relates to the injection of particulate material into the tuyere zone of a blast furnace and more particularly to a method and apparatus for preventing the compacting of particulate solids in the transfer line leading to the blast furnace.

The recently developed process for injecting particulate material into the tuyere zone of a blast furnace offers substantial economic incentives in the overall ore reduction process. It has been found, for example, that a substantial portion of the coke can be replaced by inexpensive coal when a coal-air mixture is injected into the tuyere zone of the blast furnace.

The process presently employed for injecting coal particles into the tuyere zone of a blast furnace includes admixing the particulate coal with air to form a fluidized mass of coal and air. The fluidized mass is transported through conduits to the tuyere zone of the blast furnace Where it is injected into the blast furnace during the ore reduction process. The coal particles are fed by gravity to the inlet of a coal pump or feeder. The pump impeller or rotor delivers the coal particles to an outlet that is connected to a source of air at an elevated pressure. The air picks up the coal particles and conveys the coal particles as a fluidized mass inot a transfer line. The transfer line is connected to. a splitting device which divides the fluidized mass into two equal streams. The streams are conveyed through separate conduits to injection lances located within the blow pipe in the tuyere zone of the blast furnace. The coal-air mixture flows through the lance line into the blast furnace.

One operating problem encountered in the above process in the occasional plugging of the transfer lines with coal particles. It was found if the coal feeder continues to operate after a transfer line or conduit has plugged, the entire transfer system soon becomes filled with compacted coal particles requiring a major shutdown and dismantling of the system to remove the compacted coal from the various transfer lines.

Blockage or plugging of the transfer lines is caused by several types of malfunctions. For example, the coal particles adhere to and coke on the inner walls of the lance lines, reducing the cross sectional area of the lance until a restriction or plug occurs. Blockage of the transfer line has been experienced due to foreign matter entering the transfer system with the coal and settling in the horizontal transfer lines. Although blockages from the above causes are infrequent and preventative measures can be taken to minimize their occurrence, it is highly desirable to shut down or stop the coal feeder as soon as a blockage occurs, be it in the transfer lines or in the lance pipe extending into the tuyere. If the coal feeder is permitted to continue to operate after the blockage occurs, additional quantities of particulate coal and air will be "ice injected into the transfer lines and the coal particles will form a highly compacted mass in the plugged transfer lines. Where the coal is permitted to compact in the transfer lines, considerable effort and time is required to dismantle and manually remove the compacted coal particles from the transfer lines. Where, however, the coal feeder is stopped as soon as a blockage or plug occurs, the coal particles in the transfer line are relatively free flowing and can be easily removed by opening cleanout valves and slightly shaking or hammering the downcomer from the splitter and lance lines. Special bleed connections are provided in the main transfer line as a means to remove coal particles therefrom without dismantling the piping. If, however, the coal particles are compacted in the transfer lines, other means than the bleed connections must be employed to remove the coal particles.

There is a need, therefore, for a means to shut down or stop the coal pump as soon as a blockage occurs in either the transfer lines or in the lance lines. The control means should preferably include a sensing means that does not interfere with the flow of the coal-air mixture through the various conduits. The sensing means should not be located where it is subject to the coal-air mixture. For example, any sensing device positioned in the coalair line and subjected to the coal-air mixture would quickly plug and quickly become inoperative.

It has been discovered that there is an incremental increase in the conveying air pressure on the inlet side of the coal feeder when a blockage or plug occurs in ither the transfer line or the lance lines, and a substantial decrease in the conveying air pressure on the inlet side of the coal feeder when the break occurs in the transfer line. By continuously sensing the pressure of the conveying air on the inlet side of the coal feeder and providing a control means that is actuated by the sensing means, the coal feeder can be accurately controlled to stop delivering coal particles to the transfer line when there is an abnormal increase or decrease in the conveying air pressure. The control means thus stops the feeding of additional coal particles to the transfer line when either type of malfunction has occurred. The sensing means is preferably a differential pressure device connected to both the main air blast conduit and the conveying air conduit that supplies conveying air to the coal feeder. The differential pressure device senses a variation in pressure due to either a blockage occurring in the transfer lines or the transfer line breaking and deenergizing the coal feeder.

Briefly, the invention includes a rotary coal feeder which receives a supply of particulate coal from a source by gravity or other suitable means and admixes the particulate coal with conveying air at superatmospheric pressure. The conveying air is supplied to the coal feeder from an air compresser, blower, or other suitable pressurizing device. The admixed coal and conveying air form a fluidized mass that is transported through a transfer line to a splitter device. At the splitter device the fluidized mass is divided into two equal streams and the streams are transported through secondary transfer lines to lance pipes that extend through the tuyere. The separate streams are introduced through the respective lance pipes into the tuyere zone of the blast furnace. The tuyeres also receive a supply of air from a main air blast for introduction into the blast furnace. Conventional air pressurizing and air heating means such as conven tional stoves supply the heated air for the blast furnace main air blast conveyed through the main air blast line. A differential pressure device is interconnected between the main air blast conduit and the pressurized conveying air conduit upstream of the coal feeder. The differential pressure device is connected to a switch means which is arranged to deenergize the motor that drives the coal feeder upon a predetermined pressure differential between the main air blast and the conveyor air. The pressure differential indicates either a plug or blockage in the transfer line downstream from the coal feeder or a break in the transfer line. The pressure differential device actuates the switch means to deenergize the coal feeder so that additional coal particles are not fed to the transfer line. This control means eliminates the compacting of coal particles in the transfer lines between the coal feeder and the blast furnace. As soon as the blockage has been eliminated and the pipes cleared of the settled coal particles the coal feeder is again actuated to feed coal particles and conveying air to the transfer line. This control arrangement prevents the coal particles from compacting in the transfer lines when a plug or blockage occurs. The transfer lines can quickly and easily be cleared of settled coal particles after the plug has been removed and the apparatus again restarted without substantial downtime and dismantling of the transfer line piping.

The invention is also applicable to metallurgical furnaces operating at constant pressure, for example, at atmospheric pressure. With the invention the feeder may be stopped by an increase in conveying gas pressure up stream of and adjacent the feeder above a given conveying-gas pressure.

In the accompanying drawing there is shown for purposes of ilustration one form which the invention may assume in practice. The drawing is a schematic showing of a supplementary coal feeding system for a blast furnace incorporating the novel control means for the coal injection system. It should be understood that although the system is directed to feeding particulate coal to a blast furnace, the system described can also be utilized to transport other particulate material in a gas stream.

Referring to the drawing, suitably sized particulate coal is delivered to a feeder bin 18 in a conventional manner. Located below the bin ltl are a plurality of standpipes 12 which receive the pulverized coal from the feed bin for delivery by gravity to individual coal feeders 14. It should be understood, although a gravity feed to the coal feeders 14 is illustrated, the system could, without departing from the scope of the invention, include an auxiliary feeder between the feed bin and the rotary feeder. The drawing illustrates a single coal pump 14 but it should be understood that a plurality of coal feeders are provided that are arranged to supply particulate coal to separate transfer lines. Conveying air at superatmospheric pressure is supplied from a suitable source such as a compressor 16 to a common header 13. Each coal feeder 14 has conveying air supplied thereto from the common header 18 via a branch conduit 2%. Each coal feeder 14 admixes the particulate coal fed from the standpipe 12 with the conveying air from branch conduit 20 and transfers the fluidized mass of air and particulate coal to transfer line 22.

The fluidized mass of air and particulate coal is transported through the transfer line 22 to a splitter device 24 where the fluidized mass is divided into two equal streams for delivery to secondary transfer lines 26. The transfer lines 26 are connected to lances 27 that extend into blowpipes 28 terminating short of tuyeres 259 of blast furnace 39. The two streams are delivered through the secondary transfer lines 26 to lances 27 for injection into the tuyere zone of blast furnace 30 through tuyeres 2?. The tuyeres 29 also receive hot pressurized air from bustle pipe 32 extending circumferentially around the blast furnace 3ft.

ell)

Heated air under pressure is supplied to bustle pipe 32 through hot blast main conduit 34. The hot blast main conduit 34 is supplied with air at an elevated pressure from conventional stoves, as is well known in the art. The hot air delivered through hot blast main conduit 34 and bustle pipe 32 enters the tuyere zone of the furnace through respective tuyeres 28.

Each coal feeder 14 is separately driven by an electric motor 36 and an off-on control switch schematically illustrated at 37 controls the electric motor and feeder 14. A pressure sensing means generally designated 38 is suitably connected to the control switch 37 and is arranged, as later described, to open the switch 37 and deenergize motor 36.

The pressure sensing means 38 is a conventional pressure differential device that includes a movable diaphragm and is subjected to air under pressure on opposite sides of the diaphragm. A differential in the pressure on opposite sides of the diaphragm moves the diaphragm toward the low pressure side. A suitable actuator schematically designated 39 operatively connects the movable diaphragm portion of pressure sensing means 38 and the switch means 37 so that upon preselected movement of the diaphragm a signal is transmitted through an actuator means 39 to open switch 37.

The pressure sensing means 38 has a first conduit 40 which. is connected to the hot blast main conduit 34 and subjects one side of the diaphragm to the pressure of the air in hot blast main conduit 34. The pressure sensing means 38 has a second conduit 4-2. which is connected to the branch conduit 20 adjacent the coal feeder 14. Thus, the other side of the diaphragm within pressure sensing means 38 is subjected to the pressure of the conveying air adjacent to the coal feeder 14. The pressure sensing means 33 is thus arranged to measure the pressure differential between the hot blast main conduit 34 and the conveying air conduit 20. Suitable means are provided to adjust the pressure sensing means 38 so that under normal operating conditions the pressures in conduits 4t? and 4?. balance the pressure sensing means 33. Upon a predetermined differential in pressures between the hot blast main conduit 34 and conveying air branch conduit the pressure sensing means 38 is arranged to provide an impulse or signal to actuator means 39 to open switch 37 and through conduit 44 stop motor 36 to thereby stop the feeding of coal particles to transfer line 22.

The improved control system illustrated in the drawing operates as follows. Hot blast air is supplied through main conduit 34 to the bustle pipe 32 at a preselected super-atmospheric pressure. The pressure of the air in the main conduit 34 during the reduction process remains substantially constant. Coal particles are fed by gravity through standpipe 12 from receiver it) to the coal feeder 14. Blower 16 supplies air under pressure through header 18 to branch conduits 20. As illustrated, a branch conduit is connected to the coal feeder so that the air is admixed with coal particles to form a fluidized mass that is transported through transfer line 22 to splitter 24. The blower 16, for example, maintains a pressure of approximately 45 p.s.i.g. The conveying air pressure at the inlet to the coal feeder 14, when the system is operating under normal conditions, is of the order of about 40 to 42 p.s.i.g. When a restriction or plug occurs downstream of the coal feeder 14 in the transfer lines 22, 26 or lance lines 27, the conveying air pressure on the inlet side of the pump increases to blower pressure of about 4-5 p.s.i.g. The increase in pressure due to the restriction in the conduits downstream of the coal feeder 14 is sensed by the pressure sensing means 38 and actuates switch 3'7 to deenergize motor 36 which, in turn stops the coal feeder 14. Suitable signals are provided for the operation to indicate that there is a restriction downstream of the coal feeder 14. After the restriction has been removed the switch 37 is again actuated manually and the system returned to normal operation.

Similarly, if there is a break in the transfer lines downstream of coal feeder 14, there will be a substantial decrease in the conveying air pressure adjacent the inlet to coal feeder 14. This decrease in pres-sure is sensed by the pressure sensing means 38 and also stops the coal feeder 14 in the same manner.

According to the provisions of the patent statutes, the principles, preferred construction, and mode of operation of the invention have own explained, and what is considered to represent its best embodiment has been illustrated and described. However, it should be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. A method for controlling the delivery of particulate material to the tuyere zone of a blast furnace which comprises (a) supplying a stream of hot blast air at a substantially constant pressure through a main conduit to a bustle pipe surrounding said blast furnace,

(b) feeding particulate material by gravity to a rotary feeder,

(c) supplying a conveying gas stream through a conduit to said rotary feeder at a substantially constant superatmospheric pressure,

(d actuating said rotary feeder to supply a preselected quantity of said particulate material to said conveying gas stream,

(2) admixing said particuiate material and said conveying gas stream at said feeder to form a fluidized mass,

(f) transporting said fluidized mass through conduits from said feeder to said metallurgical furnace,

(g) subjecting a pressure differential device to pressures of said hot blast air in said main conduit and said conveying gas upstream of said rotary feeder,

(h) measuring the pressure differential between both streams, and

(i) stopping the flow of particulate material to said conveying gas stream when the pressure differential between said hot blast air stream and said conveying gas stream deviates from a preselected differential in pressure.

2. A method of controlling the delivery of coal particles to the tuyere zone of a blast furnace comprising (a) supplying a stream of hot blast air at a substantially constant pressure through a main blast air conduit to a bustle pipe surrounding said blast furnace,

(b) feeding coal particles by gravity to a rotary coal feeder,

(c) supplying a conveying air stream from a source at a substantially constant superatmospheric pressure through a conduit to said rotary feeder,

(d) actuating said rotary feeder to supply pre-selected quantities of said coal particles to said conveying air stream in said rotary feeder,

(e) admixing said coal particles with said conveying 2 air stream in said rotary feeder to form a fluidized mass of coal particles suspended in said conveying air stream,

(7) transporting said fluidized mass through other conduits from said rotary feeder to said blast furnace,

(g) said conveying air stream adjacent to and upstream of said rotary feeder having a pressure supply below the pressure of said conveying air stream at said source when said fluidized mass is flowing freely through said other conduits to said blast furnace,

(11) said conveying air stream adjacent to and upstream of said rotary feeder having a pressure substantially equal to the pressure of said conveying air stream at said source when a blockage occurs in said other conduits downstream of said rotary feeder,

(i) sensing the pressure of said hot blast air in said main blast air conduit,

(j) sensing the pressure of said conveying air stream adjacent to and upstream of said rotary feeder, (k) measuring the differential in pressure between said hot blast air stream and said conveying air stream upstream of and adjacent to said rotary feeder,

(1) providing a signal when the differential in pressure between said hot blast air stream and said conveying gas air stream exceeds a predetermined amount, and

(m) said signal stopping said rotary feeder to thereby prevent coal particles from compacting in said conduits.

3. In apparatus for injecting coal particles into a blast furnace including a blast air main conduit to convey blast air to a bustle pipe surrounding said blast furnace,

(a) a rotary coal feeder,

(b) drive means for said rotary coal feeder,

(0) means to supply coal particles to said feeder,

(d) means to pressurize conveying air to a substantially constant superatmospheric pressure,

(e) a header conduit connected to said last named means,

(f) a branch conduit connecting said header conduit to said rotary feeder,

(g) said rotary feeder arranged to admix said coal particles with said'conveying air and form a fluid ized mass of said coal particles suspended in said conveying air,

(It) a transfer conduit connected to said rotary feeder and arranged to convey said fluidized mass to said blast furnace for injection into the tuyere zone of said blast furnace,

(i) the improvement comprising pressure differential means connected to said blast air main conduit and to said conveying air conduit adjacent to and upstream of said rotary feeder,

(i) said pressure differential means arranged to measure the differential in pressure between the blast air and the conveying air adjacent to and upstream of the rotary feeder, and

(k) actuator means connected to said pressure differential means and arranged upon a preselected differential in pressure between said blast air and said conveying air to deenergize said drive means for said rotary feeder and stop the flow of coal particles therethrough.

4. In apparatus for injecting coal particles in a blast furnace including a blast air main conduit to convey blast air at relatively constant superaLnospheric pressure to a bustle pipe surrounding said blast furnace,

(a) a rotary coal feeder,

(b) an electric motor to drive said rotary coal feeder,

(0) means to supply coal particles to said rotary coal feeder,

(d) compressor means to pressurize conveying air to a substantially constant superatmospheric pressure,

(e) a header conduit connected to said compressor means,

(f) a branch conduit connecting said header conduit to said rotary feeder,

(g) said rotary feeder arranged to admix said coal particles with said conveying air and form a fluidized mass of said coal particles suspended in said conveying air,

(h) a transfer conduit connected to said rotary feeder and arranged to convey said fluidized mass to said blast furnace for injection into the tuyere zone of said blast furnace,

(i) the improvement comprising pressure differential means connected to said blast air main conduit and to said conveying air conduit adjacent to and upstream of said rotary feeder,

References Cited by the Examiner UNITED STATES PATENTS iolbeek 302-28 Newhouse 30235 McGregor 7542 Hill 30217 Fahnestock 302-53 SAMUEL F. COLEMAN, Primary Examiner. ANDRES H. NIELSEN, Examiner. 

1. A METHOD FOR CONTROLLING THE DELIVERY OF PARTICULATE MATERIAL TO THE TUYERE ZONE OF A BLAST FURNACE WHICH COMPRISES (A) SUPPLYING A STREAM OF HOT BLAST AIR AT A SUBSTANTIALLY CONSTANT PRESSURE THROUGH A MAIN CONDUIT TO A BUSTLE PIPE SURROUNDING SAID BLAST FURNACE, (B) FEEDING PARTICULATE MATERIAL BY GRAVITY TO A ROTARY FEEDER, (C) SUPPLYING A CONVEYING GAS STREAM THROUGH A CONDUIT TO SAID ROTARY FEEDER AT A SUBSTANTIALLY CONSTANT SUPERATMOSPHERIC PRESSURE, (D) ACTUATING SAID ROTARY FEEDER TO SUPPLY A PRESELECTED QUANTITY OF SAID PARTICULATE MATERIAL TO SAID CONVEYING GAS STREAM, (E) ADMIXING SAID PARTICULATE MATERIAL AND SAID CONVEYING GAS STREAM AT SAID FEEDER TO FORM A FLUIDIZED MASS, (F) TRANSPORTING SAID FLUIDIZED MASS THROUGH CONDUITS FROM SAID FEEDER TO SAID METALLURGICAL FURNACE, (G) SUBJECTING A PRESSURE DIFFERENTIAL DEVICE TO PRESSURES OF SAID HOT BLAST AIR IN SAID MAIN CONDUIT AND SAID CONVEYING GAS UPSTREAM OF SAID ROTARY FEEDER, (H) MEASURING THE PRESSURE DIFFERENTIAL BETWEEN BOTH STREAMS, AND (I) STOPPING THE FLOW OF PARTICULATE MATERIAL TO SAID CONVEYING GAS STREAM WHEN THE PRESSURE DIFFERENTIAL BETWEEN SAID HOT BLAST AIR STREAM AND SAID CONVEYING GAS STREAM DEVIATES FROM A PRESELECTED DIFFERENTIAL IN PRESSURE. 